{Insert SomethingWittyHere}

The answer is: the uterus isn't what causes your period, it is effected by your period. What causes your period and what causes trans women's periods is the same thing: the endocrine system.

HRT changes the sex of your endocrine system. Feminizing HRT makes it a female endocrine system, giving us a 28-day hormone cycle just like cis women. At the end of that cycle, the hypothalamus floods the body with prostaglandins. Those are what cause all but one of the period symptoms, because they make muscles inflame and contract. They are what make the uterus shed its lining, they are what cause intestinal cramps, they are what cause body aches, they are what cause headaches and migraines. The only period symptom not causes by the release of prostaglandins throughout the body is depression, and that is caused by your endocrine system simply not processing as much estrogen and from simply feeling like shit.

So, the only symptoms trans women don't get every 28 days is menstrual cramps, because yes we do not menstruate since we don't have uteruses. But migraines, depression, body aches, intestinal cramps, and the infamous "period shits" don't exactly add up to us having any better of a time. Except we have to pretend that we're fine and nothing is different because no one believes that we get periods, not even cis women.

I thought it was normal for years to feel that way, and I don't want anybody else to suffer like I did. Trans women are likely even more vulnerable to having untreated PMDD due to a combination of difficulty accessing healthcare and the fact that cis women are refusing to share the period wisdom. (I'm not a cis woman btw, just an enby with a uterus and estrogen-dominant endocrine system.) (I'm also making the assumption that trans and cis women have equal probabilities of getting PMDD, but who knows really? I doubt anyone's ever studied it.)

While there's not much on it - something that will hopefully change! - there has been one study done that found that there is a hormonal cycle that trans women on HRT can (specifying can because tons of periods are wonky per person, who knows what folks will go through) go through that causes many symptoms "associated with the luteal phase in cisgender women".

The luteal phase is "the second half of the menstrual cycle". For people who go through menstruation, that's the part where you're sore and hungry all the time and generally annoyed (PMS symptoms).

Currently it's mostly left to anecdotal evidence - which does nothing to invalidate the experiences, everything was purely anecdotal once! - but there's likely still plenty of research being done on the topic. Hopefully we'll have some more news as time goes on!

Definitely interesting!

The reason transition is possible is because hormones are part of that environment. The reason a trans woman on estrogen can grow breasts is because estrogen flicks that switch. She already had the genes to grow breasts. So while I wasn't aware that trans women had a menstrual cycle it COMPLETELY makes sense to me that going on estrogen would turn the menstrual cycle on. Why wouldn't it? It's what hormones DO. That's their role.

Endometriosis is endometrial tissue that grows outside of the uterus, which means it doesn't go away with a hysterectomy. So you don't need a uterus to have it. Endometriosis research is in its infancy and only gaining more momentum now, but I bet there's plenty of trans women out there who have it too and have no idea because they think they have bowel issues instead (endo often grows on the bowels), or other weird symptoms they can't identify. Get on the floor on your stomach and try to do a backbend, see how it feels in your lower abdomen. When my endo was stage 4, before it got cut out, I felt a really strong and somewhat unpleasant stretch down there because my organs were alll adhered together and it didn't go away until I had the laparoscopy. Endometriosis is basically superglue around the pelvis, it makes stuff stick together instead of sliding around and you can feel ot when you try to move those organs around through a backbend.